Diazepam enhances hypericin-induced photocytotoxicity and apoptosis in human glioblastoma cells.

Glioblastoma multiforme (GBM) is neoplasm which is resistant to all currently used treatment modalities including surgery, radiation therapy and chemotherapy. Photodynamic therapy (PDT) has been suggested as a novel therapeutical approach to the treatment of malignant gliomas. Here, we attempted to enhance hypericin-induced photocytotoxicity and apoptosis by diazepam, a non-selective ligand of peripheral benzodiazepine receptors (PBR) which seem to play an important role in apoptosis regulation. For the study, we used U-87 MG and U373 MG glioma cell lines and primary cultures of GBM cells prepared from peroperatively obtained tumor specimens. The patients included 7 histologically confirmed GBMs. Colorimetric MTT assay was employed to study the photocytotoxic effects of hypericin and diazepam. Flow cytometry was used to detect apoptosis and assess the proapoptotic effects of diazepam. We found that hypericin upon photoactivation exerts strong cytotoxic effects against U-87 MG and U373 MG cells as well as primary GBM cell cultures. No cytotoxic effect of hypericin was observed under dark conditions. Diazepam inhibited cell growth in U-87 MG cells and primary cultures whereas proliferation of U373 MG cells remained unaffected. When hypericin was combined with diazepam, photocytotoxicity was increased in U-87 MG cells and primary cultures unlike U373 MG cells. Flow cytometric analysis revealed photoactivated hypericin-induced apoptosis in both cell lines. Apoptosis was significantly enhanced by diazepam in U-87 MG cells. However, no such effect was observed in U373 MG cells. In the present study, we showed that photocytotoxic effect of hypericin in glioma cells can be potentiated by diazepam. This effect is underlied by the ability of diazepam to facilitate hypericin-induced apoptosis. This work provides support to performe clinical studies involving diazepam in the antiglioma treatment regimens as an apoptosis-modulating agent.

Diazepam enhances etoposide-induced cytotoxicity in U-87 MG human glioma cell line.

Various approaches might be employed in an effort to increase efficacy of the chemotherapeutic treatment of cancer. Recently, various modulators of anticancer therapy effectiveness have been studied. Antiproliferative effects of peripheral benzodiazepine receptor (PBR) ligands might be exploited to enhance cytotoxic effect of a chemotherapeutic drug towards cancer cells. In this work, we sought to enhance cytotoxic effect of etoposide (VP-16) by a PBR ligand, diazepam (DZ) in U-87 MG human glioma cells. Cytotoxicity of VP-16, DZ and their combinations was assessed by using the microculture MTT assay. Cell survival, effective concentrations (EC) and the onset of cytotoxic effect were determined. After 72 h of cultivation, survival of U-87 MG cells was reduced to 57 +/- 7% in the presence of VP-16 at 12.5 microg/mL alone, whereas DZ at 10-4 mol/L alone caused 28 +/- 6% reduction in cell survival. Coincubation of VP-16 at 12.5 microg/mL with DZ at 10-4 mol/L led to a further decrease in cell survival to 45 +/- 6%. Furthermore, DZ at 10-4 mol/L significantly decreased effective concentrations, EC10, EC30 and EC50, of VP-16 and the dose-response curves were shifted to the left. Addition of DZ at 10-4 mol/L to VP-16 also facilitated the onset of its cytotoxic effect. The same decrease in survival was thus achieved approximately 30 h earlier in comparison with VP-16 alone. However, DZ at 10-9 mol/L failed both to exert any effect on glioma cells survival and enhance cytotoxic effect of VP-16. DZ at 10-4 mol/L was capable of both reducing U-87 MG glioma cells survival when applied alone and also enhancing the cytotoxic effect of VP-16. No such observation was made for the lower concentrations of DZ. Potential implementation of diazepam in the antiglioma/anticancer armamentarium awaits further experimentation but phase I and phase II clinical trials could be suggested.

[Calorimetric evaluation of directly compressed tablets]. / Kalorimetrické hodnocení prímo lisovaných tablet.

The paper studies the effect of the type of the disintegrating substance and the lubricant on the destruction heat of tablet materials and tablets. Destruction heat was determined by means of isoperibolic calorimetry. Tablet materials and tablets contained Avicel PH 101 as the dry binder, 10% of Primojel, Ac-Di-Sol, or Polyplasdone XL as disintegrating substances, and 5% of magnesium strearate or sodium laurylsulfate as the lubricants. The sum of destruction heats of the individual auxiliary substances equalled the found values in tablet materials and tablets. In tablets, in contrast to tablet materials, values of destruction heat higher by 57.9% were found. In the disintegrating substances and lubricants tested, the found values of destruction heats were dependent on the values of destruction heats of the individual auxiliary substances. In the disintegrating substances, a linear dependence of the total destruction heat (CDT) on the destruction heat of the disintegrating substances (DTR) was found, given by the relationship CDT = 0.797.DTR + 17.666 with the correlation coefficient r = 0.986.